Effect of titanium dioxide nanoparticles on gamma-ray treatment of phenol in different matrices: implications in toxicity toward Daphnia magna

Gamma-ray treatment of phenol was studied in terms of both chemical degradation and toxicological change. About 90% of phenol (5.0 × 10(-4) M) in ultrapure water (UW) was eliminated by gamma-irradiation at a dose of 10 kGy, but acute toxicity was dramatically increased, particularly for dose of 1 kGy, due to the formation of more toxic by-products such as hydroquinone, benzoquinone, resorcinol and catechol. The addition of TiO(2) nanoparticles had little effect on the removal of phenol in UW, but substantially enhanced the mineralization of phenol compared with gamma-irradiation alone. Additionally, degradation of phenol by gamma-irradiation was inhibited in a wastewater effluent (WE) matrix, likely due to the presence of dissolved organic carbon (22.06 mg L(-1)). Furthermore, lower concentrations of toxic by-products were generated both in WE and in the presence of TiO(2) nanoparticles, resulting in reduction of toxicity increase by gamma-irradiation. Meanwhile, the toxicity of gamma-ray treated phenol in WE was well estimated with simple summation of individual toxicity of phenol and by-products (R (2) = 0.9678).

Radiolysis of aqueous 4-nitrophenol solution with Al2O3 or TiO2 nanoparticles

Aqueous 4-nitrophenol solutions containing TiO2 or Al2O3 nanoparticles were irradiated with electron beam. 4-Nitrophenol was decomposed by the ionizing radiation process in the absence of the nanoparticles. The addition of TiO2 or Al2O3 (2 g l(-1)) before irradiation improved the removal of 4-nitrophenol, total organic carbon (TOC) but also nitrogen (TN). To identify the origin of the loss (catalysis or simply adsorption), TiO2 or Al2O3 nanoparticles were added after irradiation. Experiments show that the effect of the presence of TiO2 or Al2O3 during irradiation is just due to adsorption.